**Retro Review: Garrett CM 20 Calculator**

**Introduction**

Is it Pac Man or is it a calculator? |

I bet if Pac
Man and Ms. Pac Man ever used a calculator, it is this one: the Garrett CM 20
calculator. I received this calculator
as a present from my good friend Chris Brame in Illinois. Many thanks and appreciation, and it is hit with
the household.

There is close
to no information for the Garrett CM 20, only to find that model originated in
1973, predating the famous Pac Man game by seven years. On the bottom label, the Garrett Comtronics
Corporation is located in San Diego, California. The CM 20 was made in the United States.

The CM 20 is AC
powered, with the power switch on the back of the calculator.

**A Spherical Delight**

The
CM 20 comes has a spherical design.
Garrett also produced several calculators with a spherical design, the
CM 25 and CM 35. The CM 25 has memory
functions.

The
keyboard on the CM 20 is just a delight; the keys are light to the touch and
easy on the fingers. Also, the keys are
responsive.

Check
out the display, the digits are orange!

**The A/B and % Keys**

The
CM 20 is a real basic four function calculator, without memory or a square root
key. However, the CM 20 has an A/B key,
which works as a “Last X” key (think scientific keystroke programmable
calculators from Hewlett Packard). After
a pending operation completes (+, -, *, or ÷), press the A/B key to recall the
last number entered before completing the operation. For example:

6
[ + ] 3 [ = ]
(Display: 9) Pressing [A/B] recalls 3 (and puts 9
in the temporary register)

3
[ + ] 6 [ = ] (Display: 9)
Pressing [A/B] recalls 6 (and puts 9 in the temporary register)

75
[ ÷ ] 15 [ = ] (Display:
5) Pressing [A/B] recalls 15.

And
so on.

The
percentage key works a little bit different from most four-function
calculators. On the CM 20, you are
required to press the equals key to complete the operation. To find out a percentage of a number, enter
the base, press any of the arithmetic keys, the percentage and the % key. To illustrate:

25
[ + ] 15 [ % ] (Display: 3.75) [ = ]
(Display 18.75 = 25 + 15%)

25
[ - ] 15 [ % ] (Display: 3.75) [ = ]
(Display 21.25 = 25 – 15%)

25
[ * ] 15 [ % ] (Display: 3.75) [ = ]
(Display 93.75 = 25 * 3.75 = 25 * (25 * 15%))

25
[ ÷ ] 15 [ % ] (Display: 3.75) [ = ] (Display 166.66666 = 25
/ 0.15)

25
[ + ]/[ - ]/[ * ]/[ ÷ ] 15 [ % ] Stop.
(Display: 3.75 = 25 * 15%)

**Final Verdict**

This
calculator is going to be on my desk for a long time. I love the retro 1970s design and the
spherical shape of the calculator. Thank
you Chris!

Eddie

This
blog is property of Edward Shore, 2017